1. Field of the Invention
This disclosure relates, in general, to a brake cylinder piston travel calculating system and, more particularly, to the use of the electrically controlled pneumatic (ECP) brake control system to determine the distance traveled by the brake cylinder piston.
2. Description of Related Art
49 C.F.R. §232.205(c) provides the tasks and requirements for a Class 1 terminal brake test for a train. Minimum brake cylinder piston travel of truck-mounted brake cylinders must be sufficient to provide proper brake shoe clearance when the brakes are released. In addition, piston travel must be inspected on each freight car while the brakes are applied. More specifically, 49 C.F.R. §232.205(c)(5) requires that “[f]or cars equipped with . . . 10-inch diameter brake cylinders, piston travel shall be within 7 to 9 inches. If piston travel is found to be less than 7 inches or more than 9 inches, it must be adjusted to nominally 7½ inches. For cars not equipped with . . . 10-inch brake cylinders, piston travel shall be within the piston travel stenciled or marked on the car or badge plate.”
Freight trains typically undergo the pre-departure Class 1 terminal brake test prior to the train being cleared to proceed from the train make-up yard. Currently, such an inspection requires a trainman to “walk the train” visually checking each car's brake equipment. Prior art type truck mounted brake assemblies include a piston travel indicator attached to the brake cylinder assembly for monitoring piston travel to determine whether or not the brake equipment is functioning properly.
One type of currently used piston travel indicator comprises an indicating means, such as a flag, which moves along a measuring means. This measuring means has an acceptable operating range or zone marked thereon. The inspector views the location of the flag with respect to the acceptable operating range to determine whether or not the braking equipment is functioning properly. For example, if the flag is below the range, then this would indicate that the slack adjuster trigger needs to be adjusted. If, on the other hand, the flag is above the range, this could indicate that either the slack adjuster is out of capacity and the brake shoes are too worn or the slack adjuster is not functioning properly and requires maintenance. Due to the location of this piston travel indicator within the truck mounted brake assembly underneath the car, it is often difficult for the trainman to readily view the indicator and to make a proper determination as to the functioning of the braking equipment. Thus, it becomes burdensome to inspect the braking equipment of the train and consequently more time consuming to complete the terminal test.
An improvement to such prior art systems is disclosed in U.S. Pat. No. 6,364,068 to Ring et al. This patent describes a brake cylinder piston travel indicator that monitors an amount of piston travel in a brake cylinder assembly in a railway braking system. The railway braking system includes a brake beam and a brake cylinder piston within the brake cylinder assembly which is in engagement with an end of a brake cylinder force transfer lever. The brake cylinder piston travel indicator includes a rod member that is rotatably secured to and extends substantially parallel with at least a portion of the brake beam. A member is provided which operationally interconnects the rod member with the cylinder force transfer lever and is capable of transferring a rotational force to the rod member. This rotational force is caused by activation of the piston in the brake cylinder assembly. An indicating device is provided which is engagable with a first end of the rod member and is capable of responding to the rotation of the rod member and indicating an amount of travel of the piston during activation thereof in the brake cylinder assembly. However, this system continues to require train inspection personnel to visually inspect the brake cylinder to determine the travel distance, thereby making the system susceptible to human error.
Accordingly, a need exists for a system that automatically determines the distance traveled by the brake cylinder piston without the need for visual inspection.